Decrease default pull timeout to 2 seconds.

This can result in more pull failures, but can prohibit slow pullers
from slowing down statsd.

Test: atest GtsStatsdHostTestCases
Test: atest statsd_test
Test: atest FrameworkStatsdTest
Bug: 154056912
Change-Id: Ie30bd3584d808bb11aaaf0fe2057c9adfb198644